The present invention pertains generally to an alarm clock. More particularly, the present invention pertains to an alarm clock having an ambient light detector for controlling the illumination of the alarm clock display.
Alarm clocks are well known timekeeping devices which generate an alarm sound at a preselected time of day. Generally, the alarm is sounded at a preselected time of day corresponding to the time at which a user must wake up from a night's sleep.
There are known alarm clocks which have a time displaying section that is illuminated only when an illumination switch is turned on. Thus, for example, if the illumination light bothers the user (such as when the user is trying to fall asleep), the illumination switch can be manually turned off to darken the alarm clock time displaying section.
It is also known to provide a light sensor, such as a cadmium sulfide photosensor, which detects ambient light. The illumination of the time displaying section of the alarm clock is thus controlled depending on the ambient light detected by the photosensor. Therefore, when the room is dark, such as at night, the photosensor detects a dark condition and the time displaying section is illuminated so that it is visible in the dark room. If the alarm clock is battery operated, the battery will not unnecessarily drain during light conditions, when there is no need for illumination of the time displaying section.
If an illumination switch is used to turn the illumination of the time displaying section on and off, the user must either leave the illumination of the time displaying section on (which may cause trouble to the user while trying to get to sleep), or the user must manually shut the illumination switch off. However, if the user does manually shut the illumination switch off, it must then be manually turned on again in order to observe the time displaying section in a darkened room. Therefore, if the user wakes up at night and wishes to know what time it is, the illumination switch must be first found, and then switched on in the dark.
On the other hand, if the alarm clock has a photosensor, since the illumination of the time displaying section is kept turned on when the room is dark, the battery will be drained unnecessarily to provide the illumination. Also, since the time displaying section is illuminated whenever the room is dark, the illumination may bother the user while trying to fall asleep.